Many apps receive updates that remove support for old versions of iOS. Some publishers even block installations on older versions of iOS!
I hope to have a list or chart with the last compatible builds of various apps for the different versions of iOS that I've used.
Example:
| iOS Version App & Version |
iOS 4.1 | iOS 4.2.1 | iOS 5.1.1 | iOS 6.1.6 |
| Angry Birds | 2.3.0 | 2.3.0 |